I bought movie tickets from one of those automated ticketing kiosks last weekend. While the user interface certainly won’t win any design awards, it seems pretty functional. But one screen always sticks out to me: the part where it asks you to swipe your loyalty card. This would be fine, except I don’t have such a card. The only button on the screen says “Continue”, and I always get stuck reading the instructions before I figure out that you’re supposed to press that button even if you don’t have a loyalty card.

This is a perfect example of a common user interface mistake that you see on websites, kiosks, consumer electronics, and more. The designers make an assumption that they think will simplify the process, but it ends up slowing people down. In the case of the ticketing kiosk, they really ought to say “Do you have our loyalty card?” and present buttons for Yes and No. For those who choose Yes, it could then prompt you to swipe the card. Or, to keep the workflow that I think they were aiming for, just change the existing button to say “I don’t have a loyalty card”. This would eliminate any confusion.

Whenever you’re designing for an audience of diverse users, think carefully about any assumptions you make. If some customers don’t have a special card, or a password, or a membership number, your design shouldn’t assume that everyone has this data. And even if you can’t remove these data capture screens from your application, at least make it easy for people to bypass them when they don’t have the information that you’re asking for. In most cases, asking customers the right question with a simple Yes or No response can work wonders.